This disclosure relates generally to light emitting diodes (LED) dice and more particularly to light emitting diode (LED) dice having wavelength conversion layer and to a system and method for fabricating light emitting diode (LED) dice with the wavelength conversion layers.
Light emitting diode (LED) dice have been developed that produce white light. In order to produce white light, a blue (LED) die can be used in combination with a wavelength conversion layer, such as a phosphor layer formed on the surface of the die. The electromagnetic radiation emitted by the blue (LED) die excites the atoms of the wavelength conversion layer, which converts some of the electromagnetic radiation in the blue wavelength spectral region to the yellow wavelength spectral region. The ratio of the blue to the yellow can be manipulated by the composition and geometry of the wavelength conversion layer, such that the output of the light emitting diode (LED) die appears to be white light.
One method for forming the wavelength conversion layer in a light emitting diode (LED) die is to fabricate the wavelength conversion layer as a separate member, which is then attached to the die. For example, the wavelength conversion layer can be in the form of a piece of tape having a phosphor compound thereon, which is placed on an adhesive layer deposited on the light emitting diode (LED) die. Typically, the wavelength conversion layer is initially fabricated on a substrate and is removed from the substrate and attached to the die using a capillary device attached to a vacuum supply.
Referring to FIG. 1, a prior art system for handling wavelength conversion layers includes a plurality of wavelength conversion layers 10 contained on a substrate 12 with an adhesive tape 14 attaching the wavelength conversion layers 10 to the substrate 12. For removing the wavelength conversion layers 10 from the substrate 12, a capillary device 16 can be used in combination with an ejection pin 16. However, due to the adhesiveness of the tape 14, removal of the wavelength conversion layers 10 from the substrate 12 requires a large force. As illustrated in FIG. 2, this can cause cracks 20 or other damage to the wavelength conversion layers 10, which can vary the color composite of the white light produced by a light emitting diode (LED) die.
It is difficult to fabricate a white light emitting diode (LED) die with consistent color balance because any damage to the wavelength conversion layer during the fabrication process can change the output of the die. The present disclosure is directed to a system and method for fabricating light emitting diode (LED) dice in which damage to the wavelength conversion layers is minimized.